Messed-up mitochondrial DNA
Hi, this is my mum, and this is my dad, and this is my other mum...
Okay so it probably wouldn’t play out like that, but three biological parents could be close to reality.
Mitochondria are the body’s energy factories. It is here that the Krebs cycle (a.k.a. citric acid cycle) and oxidative phosphorylation (electron transport chain and chemiosmosis) take place. The Krebs cycle generates some ATP, but also NADH and FADH2 and during oxidative phosphorylation these two molecules generate the greater proportion of ATP molecules made through cellular respiration. ATP molecules are the chemical unit of energy in the body. We do make ATP molecules outside the mitochondria during anaerobic respiration, but not very many, leading to only little energy production.
So, we use mitochondria to produce the energy demands we put on our body. The trouble is, mitochondria have their own DNA.
It is thought that mitochondria were once free-living bacteria that got caught up in a host cell. With the cell providing the raw materials, the mitochondria boosted the cell’s capacity to make ATP molecules. Fast-forward to today, and mitochondria are a part of every one of us.
But, they still have their own DNA, distinct from the nuclear DNA that governs how our bodies are put together. And this mitochondrial DNA is much less stable than nuclear DNA, accruing random mutations 1,000 times faster. These mutations affect up to 1 in 5,000 children. These children are born with diseases which primarily affect parts of the body that are thirsty for energy, like the brain and muscles.
Now there are procedures, called three-person in vitro fertilisation (IVF), which attempt to get around the issue of mitochondrial DNA mutations. Nuclear genetic material from the egg of a woman with mutant mitochondria is transferred into another woman’s egg. The technique has been tested in mice, in monkeys, and in human egg cells in culture. Will it one day be used on humans?
Stay tuned...